Vania



H. A. PEDR I CK AND G. F. KOLB. METHOD OF MARING PISTON RINGS.

APPLICATION FILED OCT- H. 1918.

Patented Oct. 28, 1919.

UNITED STATES PATENT OFFICE.

HOWARD PEDRICK, OF BALA, AND GEORGE F. KOLB, OF PHILADELPHIA, PENNSYL- VANIA, ASSIGNORS TO HOWARD A. PEDRICK AND ALBERT D. PEDRICK, COPARTNERS TRADING AS PEDRICK TOOL AND MACHINE COMPANY.

METHOD OF MAKING PISTON-RINGS.

Specification of Letters Patent. 7

Application filed October 17, 1918. Serial No. 258,642.

of makingpiston rings which when placed in a piston within an engine cylinder, shall exert a uniform pressure upon the cylinder wall at all points of their peripheries and thus reduce to a minimum the leakage past the piston as well as prevent uneven wear of the cylinder walls.

These objects and other advantageous ends we attain as hereinafter set forth, reference being had to the accompanying drawings, in which,

Figures 1 and 2 are respectively a side elevation and a plan of the templet used in carrying out our invention;

Fig. 3 is a vertical section of the upper die and plunger also employed in connection with-our invention; and

Fig. 4: is a vertical section of the lower d1e with a ring made in accordance with our invention. As a result of considerable experimen we have found that a cast iron piston rlng which throughout its periphery exerts a unlform pressure against the cylinder wall of an engine, upon release from such cylinder, will assume a shape determined by the laws of beams under load. Conversely, if a ring he formed with such a shape as that above indicated, it will, when placed in an engine cylinder, exert a pressure which 1s uniform at all vpoints of its periphery and if a split circular ring is acted on throughout its periphery by uniform outward'radial pressures, the shape which it will then assume is that which a ring must possess if it is to assume a circular form when placed in a' cylinder and subjected to uniform inward radial .pressures.

point at which the split is made, the compressive stress resulting from this deflection Patented 0ct.28,1919.

is equal in all parts of the ring and conse- 4 quently the radial component of the force exerted by the internal stress in the ring will be uniform throughout its periphery. Moreover the shape assumed by the ring is that required to cause itto exert a uniform outward pressure at all points when compressed into the form of a circle.

' In order therefore, to make a ring capable of exerting a uniform outward pressure at all points of its periphery upon the wall of an engine cylinder, when it has been compressed into circular form in the grooveof a piston, we first split a circular cast iron ring 1 and by the application of-opposite forces applied tangentially to its ends, spring these apart sufficiently to introduce a spacing piece 2. When so expanded the ring possesses the shape required to impart to it the above noted desirable characteristics ;the length of the spacing piece 2 .being varied as may be found advisable to cause the finished ring to press outwardly spacing" piece 2 between its ends will perfectly fit into it. The die 3 upon completion is preferably mounted upon a second and heavier ring 4 whose internal diameter is less than that of the opening through said die, there being mounted upon it a spring actuated ejecting ring forming an annular shoulder 5 for holding the blanks from which piston rings are to be made.

For coacting with this die we provide a I plunger 6 having suitably attached to its lower end a head 7 whose body 8 is of such form or outline that it will perfectly fit within the templet ring 1 when the spacing piece 2 is inserted between its ends. 7

Below the body 8 the head 7 is formed with a tapering portion 9 whose lower end is preferably circular and whose upper end has the same outline as that of the body 8. Between the body 8 and the main portion of the plunger is mounted a ring 10 whose external diameter is such that it serves as a flange for the body beyond which it projects. The body and this ring are held together in any suitable manner as by screws 11 and are in turn held to the plunger 6 by a nut 12 threaded upon the correspondingly threaded lower end of the latter.

In carrying out our method, a split circular cast iron ring blank 00 of the proper diameter (that of the templet ring 1 before being expanded by the spacing piece 2) is heated to redness and placed in the die 3 so as to rest upon the shoulder 5 thereof it being understood that said die, as well as the head 7 and plunger 6 are mounted on the anvil and reciprocating head respectively of a suitable press. The plunger 6 is then lowered to cause the tapering end 9 of the head 7. to enter the ring and expand it until when it has passed through and the body 8 has been entered in it, said ring will exactlv conform to the shape of the opening through the die 3.

The ring when heated as above is practically plastic and retains the shape then given until it is quenched or cooled after removal from the die. \Vhen so cooled it will be found to possess the form theoretically required in order that it shall exert on the cylinder walls of an engine an outward pressure which is uniform at all points of its length. It will be understood that in placing the heated blanks in the die 3-4, the cut or split of each of them must always occupy the same definite position as indicated by a suitable mark 13 on the die so that its ends when separated by the plunger head 7, will occupy the same positions as would the ends of the templet ring 1 if the latterwere placed Within said die.

We claim:

1. The method of making a piston ring which consists of forming a templet having the outline assumed by a split ring when its A ends are subjected to opposite tangential forces; heating a split blank ring; causing said heated ring to assume the shape of the templet; and cooling said latter ring.

52. The method of making a piston ring which consists in placing a spacer between the ends of a split ring and operating on a split blank ring to cause it to assume and retain the same external shape as said first ring.

3. The vmethod of making a piston ring which consists in forming a templet having the outline assumed by a split ring when its ends are subjected to opposite tangential forces; making a die of the same shape as said templet; and causing a heated split blank ring to be acted on by said die to give it the form thereof.

4. The method of making a piston ring which consists in inserting a spacer between the ends of a split ring; making an annular die of the same shape as that of said ring; heating a blank split ring; expanding said heated ring in the die to cause it to conform thereto; and cooling the finished ring.

5. The method of making a piston ring which consists in inserting a spacer between the ends of a split ring; making a die of the same shape as said ring; and forming a blank in said die to cause it to assume and retain the. desired shape. i

6. The method of making a piston ring which consists in applying equal and opposite tangential forces to the ends of a split ring to expand the same; making two 00- operating die members to fit the internal and external curves of said ring; and forming a heated split ring by said die members to cause it to assume and retain the shape of said expanded ring.

7. The method of making a piston ring which consists in giving a split ring the form assumed when it is subjected to a uniform outward radial pressure; forming a die of the same shape as said ring; and forming a heated split blank ring to give it the shape of said die.

In witness whereof we affix our. signatures.

HOWARD A. PEDRICK. GEORGE F. KOLB. 

